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By S. Suphi Yavasca, A. M. Gaudin

THIS paper is intended as a contribution to our knowledge of the mechanism of comminution and of the work of crushing. In a previous paper' it was shown that with quartz comminution proceeds as follows I. The size distribution of broken fragments made by a single fracture is such that the new surface on each grade is the same. 2. Multiple fracturing results in a size distribution such that in the fine sizes the surface per grade is the same in every grade; in coarse sizes the surface per grade decreases gradually with increasing size. In that paper it was mentioned that determinations on minerals other than quartz were in course of completion in order to establish the generality of these observations. In this paper, condensed data2 are presented for galena, pyrite and glass. Galena and pyrite are crystalline material and glass is noncrystalline. Galena has excellent cubic cleavage. Pyrite, although cubical, does not have marked cleavage. Quartz, on which the original determinations were made, does not cleave and although crystalline (hexagonal) breaks conchoidally. Glass breaks much like quartz. It is apparent, therefore, that the minerals selected represent some range in character of the solid without covering all possible types. GLASS Fifteen glass marbles were crushed individually in the pendulum crusher described in the preceding paper,1 then subjected to careful screening for 30 min. Six sized fractions were selected and cleaned in a hot 0.12 N solution of hydrochloric acid, washed with distilled water and dried on a hot plate. This was followed by an examination with a binocular microscope, to remove foreign matters not eliminated in cleaning as well as to eliminate "compacts" of fine particles. These compacts are groups of fine iragments that seem to be mechanically stuck together as a result of localized compacting during the comminution operation. The presence and the abundance of these compacts may be related to the amount and direction of the forces applied in different crushing devices. Since, properly, such compacts should be entirely eliminated in the sizing analyses, it is necessary to remove them to the last before making surface determinations on sized fractions. For example, with a - 28 + 35-mesh glass the surface areas of two samples, one cleaned with acid and under the binocular, the other only washed, were 102 and 172 sq. cm. per gram, respectively. Examination of the samples under an Ultropak microscope showed that washing alone failed to remove the compacts and also that it fails to remove certain fine dusts attached to the particles. Cleaning with acid loosens the fine dusts and

Jan 1, 1945

By Walter L. Maxson, Fred C. Bond

SINCE the last publication of tabulated results of grindability tests by the authors1 the total number of ball-mill tests made has more than doubled, and rod-mill tests have become increasingly important. Nearly all of the standard closed-circuit ball-mill and rod-mill tests made to date are included in the present tabulation, together with additional information not previously published. STANDARD BALL-MILL GRINDABILITY TESTS The method of conducting these closed-circuit tests has not been altered. A sample of the ore or other material is stage-crushed in rolls set at 1/16-in. opening with a 6-mesh screen until all of it has passed the screen. The combined minus 6-mesh screen undersize is mixed, sampled and screen-analyzed, and its apparent specific gravity is determined by packing and shaking in a standard container, and weighing. The apparent specific gravity ordinarily is about 60 per cent of the true specific gravity. The unit volume present in the mill in all tests is 700 c.c. of the packed minus 6-mesh roll product, and the number of grams occupying 700 c.c. is the unit test weight. This weight is placed in the mill dry, ground for the number of revolutions estimated to be necessary, discharged, and screened mechanically in three testing sieves of the mesh size at which the test is to be conducted. The oversize, or circulating load, is weighed, sufficient fresh minus 6-mesh feed is added to bring the total weight up to that of 700 c.c., and the charge is returned to the mill for a second grinding period. All standard ball-mill tests are conducted at 250 per cent circulating load, and the number of revolutions in the mill necessary to obtain this circulating load at any grinding period is estimated from the results of the previous period. The number of net grams of screen undersize produced per revolution of the mill approaches its final equilibrium value after several grinding periods, and this is recorded as the grindability, or relative ease of grinding, of the sample. A cylindrical ball mill, 12 by 12 in. inside, with a smooth lining and rounded corners, is used with a revolution counter. Under standard grinding conditions it runs at 70 r.p.m., and contains a charge of 285 iron balls weighing 20,125 grams, ranging from I ½ to ¾ in. in diameter. Tests are conducted at the mesh size to which the ore is to be ground in practice, and the capacity to be expected from a given mill is calculated by comparing the

Jan 1, 1943

By Holbrook G. Botset

It is possible by means of the electrolytic model to simulate water-flooding or gas recycling systems involving input and output wells, and also the encroachment of a natural water drive. The results are obtained pic-torially, and by simple measurements and calculations the percentage of recovery is obtained qualitatively as a function of the total input. Introduction The increased demand for petroleum products, together with the decline in discovery rate and the higher cost of recovery as deeper formations are brought into production, has stimulated interest in methods for studying and predicting efficiencies of various production programs. Among methods Of recovery that have become of increased significance recently are gas recycling in condensate fields and secondary recovery by water-flooding. The electrolytic model is a useful device for studying such methods in the laboratory, at least in a qualitative way. The original experiments with electrolytic models and the development of their application to the study of secondary reCoverY problems were published in 1933. 1,2,3 Subsequently other investigators continued the development and modification of the bait method, with resultant improvements and extension of its applications.4-7 The method and equipment to be described here are thought to represent still further improvement in the results obtainable, with increased validity in their application to field problems. Sand OF Principles of Operation The underlying theory of the operation of the model is given in references I, 2 and 3. However, a brief statement of principles involved is given herewith. The applicability of the model is based on the fact that Ohm's law and d'Arcy's law are exactly analogous; whence, electrical flow through a conducting medium may be used to simulate homogeneous fluid flow through a permeable medium. If two electrodes are placed in a conducting (ionized) solution and connected to the positive and negative terminals of a source of direct current, the positive ions of the solution will move toward the negative terminal, Since the velocity of an ion in an electrolytic medium is proportional to the electrical gradient, just as the velocity of a fluid particle in a porous medium is proportional to the pressure gradient, the motion of the ions in the potential field will be the same as the motion of fluid particles in a porous medium if the positive and negative terminals (input and output wells) and boundary conditions are made equivalent in shape and distribution. In order for the analogy to hold exactly, the sand must be assumed to have uniform porosity and permeability and the input

Jan 1, 1946

By Holbrook G. Botset

It is possible by means of the electrolytic model to simulate water-flooding or gas recycling systems involving input and output wells, and also the encroachment of a natural water drive. The results are obtained pic-torially, and by simple measurements and calculations the percentage of recovery is obtained qualitatively as a function of the total input. Introduction The increased demand for petroleum products, together with the decline in discovery rate and the higher cost of recovery as deeper formations are brought into production, has stimulated interest in methods for studying and predicting efficiencies of various production programs. Among methods Of recovery that have become of increased significance recently are gas recycling in condensate fields and secondary recovery by water-flooding. The electrolytic model is a useful device for studying such methods in the laboratory, at least in a qualitative way. The original experiments with electrolytic models and the development of their application to the study of secondary reCoverY problems were published in 1933. 1,2,3 Subsequently other investigators continued the development and modification of the bait method, with resultant improvements and extension of its applications.4-7 The method and equipment to be described here are thought to represent still further improvement in the results obtainable, with increased validity in their application to field problems. Sand OF Principles of Operation The underlying theory of the operation of the model is given in references I, 2 and 3. However, a brief statement of principles involved is given herewith. The applicability of the model is based on the fact that Ohm's law and d'Arcy's law are exactly analogous; whence, electrical flow through a conducting medium may be used to simulate homogeneous fluid flow through a permeable medium. If two electrodes are placed in a conducting (ionized) solution and connected to the positive and negative terminals of a source of direct current, the positive ions of the solution will move toward the negative terminal, Since the velocity of an ion in an electrolytic medium is proportional to the electrical gradient, just as the velocity of a fluid particle in a porous medium is proportional to the pressure gradient, the motion of the ions in the potential field will be the same as the motion of fluid particles in a porous medium if the positive and negative terminals (input and output wells) and boundary conditions are made equivalent in shape and distribution. In order for the analogy to hold exactly, the sand must be assumed to have uniform porosity and permeability and the input

Jan 1, 1946

By E. T. Turkdogan, P. Grieveson

Experimental results are given for the rate 0.f solution of nitrogen in y iron in the temperature range 1000° to 1200°C. It is shown that, when purified reacting gas is used, the rate-controlling process is the diffusion of nitrogen into the iron. The difhsiuity of nitrogen in y iron is calculated from the results and the equation logD = —(8800/T) — 0.04 is recommended to represent the temperature dependence of the diffusivity. In some experiments using unpurified nitrogen, solution rates are found to be slower than those attributable to a solely solid-state diffusion process. Indications are that in the presence of impurities in the gas, e.g., H,O, chemisorption of nitrogen at the surface is hindered and becomes a rate-controlling process for the transfer of nitrogen across the gas -metal interface. ALTHOUGH the solubility of nitrogen in y iron at known nitrogen activities has been well-established,'-a the kinetics of the solution of nitrogen in iron are not known. The work of Darken, Smith, and Filer' indicates that at temperatures below about 1300°C the rate of solution of nitrogen in y iron is controlled by a chemical reaction at the metal surface, while at temperatures above about 1300°C the rate-controlling process is the diffusion of nitrogen in the metal. Fast and verrijps studied the denitro-genization of y iron using wet hydrogen at 950°C and their results clearly indicate that the rate of nitrogen removal is controlled by diffusion of nitrogen in the metal. In Part I of this series of papers, the kinetics of the solution of nitrogen in y iron are discussed in the light of the present experimental work. EXPERIMENTAL Apparatus. The reaction chamber consisted of a platinum wire-wound resistance furnace with a re-crystallized alumina reaction tube. The temoerature of the furnace, which was automatically controlled to approximately 1°C, was measured with a Pt/Pt-13 pct Rh thermocouple and a potentiometer. The temperature distribution in the working zone of the furnace was determined using a calibrated Pt/Pt-13 pct Rh thermocouple and the hot zone was found to be approximately 3 in. long with a temperature variation of * 3°C. A series of experiments was also carried out at 1000°C and pressures above atmospheric using a pressure vessel which was similar in construction to that described elsewhere.1° Materials. Ferrovac E grade iron used in all ex-

Jan 1, 1964

By T. Sterry Hunt

THIS remarkable mine, to which attention has lately been drawn, is situated not far from the New River, in Ashe County, North Carolina, on a spur of the Blue Ridge which lies between the main crest of this name and the so-called Iron Mountain, a part of the Unaka or Smoky Mountain range. It is on a true fissure-lode, which cuts the strata of gneiss and mica-schist of the region. These, which have the lithological characters of what I have called the Montalban or White Mountain series, have here a dip of about forty-five degrees to the southeast, while the lode is vertical, with a course north 60° east. Both the country-rock and the lode, as is usual in this region, are decomposed to considerable depths ; and the latter exhibits a cap of hydrous peroxide of iron or gossan, blocks of which, left by the denudation of the softer inclosing rock, are scattered over the surface, and first called attention to the locality as a source of iron ore. In sinking upon this lode, it was found that the porous gossan at a certain depth became charged with carbonate and red oxide of copper, and lower down was replaced by sulphuretted ores of this metal of remarkable richness. This deposit was worked for copper, in an irregular manner, before the late civil war, but was afterwards abandoned, and only reopened during the present year, by Messrs. S. S. & J. E. Clayton, of Baltimore. The outcrop has been traced for 1900 feet, and the sulphuretted copper ores have been met with in five shafts in a distance of 661 feet, a drift having moreover been carried for the above distance through the solid ore. The breadth of the lode, so far as opened, varies from six to eight feet to fourteen feet in places, and that of the outcrop of gossan is, in some parts, twenty feet. After comparing this deposit with the copper mines of Ducktown, Polk County, Tennessee, and those of Carroll County, Virginia, it is evident that we have, at Ore Knob, to do with the same kind of black ores as were met with in these mines, and will be noticed further on. Beneath the gossan, at Ore Knob, is found, in some parts, an iron-black, friable, drusy, crystalline, sulphuretted ore, inclosing grains of quartz, garnet, and magnetite, besides a black non-magnetic mineral, not attacked by nitric acid. This ore contains about 36 per cent. of copper, and portions have the mineralogical charac-

Jan 1, 1874

By T. Sterry Hunt

BUT little was known of the coals of Southeastern Ohio until the present survey of the State under Dr. Newberry began its work. The results of the geological investigations of Prof. E. B. Andrews in this region, and of the chemical investigations of Prof. T. G. Wormley, both of which appear in the reports of the survey for 1869 and 1874, and more recent special reports by the former, together with some data for which I am indebted to the kindness of Dr. Newberry, and my own limited observations, have served me for the preparation of the following notice of the coals lying on the western border of the great Appalachian coal-basin in the region drained by the Hocking River and its tributaries, and belonging to the Lower Coal-Measures. Some uncertainty exists as to the place in the succession of the lower coals to be assigned to the seams known and mined in the Hocking Valley. It is the opinion of Prof. Andrews that the inequalities of the original surface were such that we cannot identify in that region the lowest coals known in Northwestern Pennsylvania and the contiguous parts of Ohio, but that we must rather count from above downwards. These conclusions Dr. Newberry is not prepared to accept, and further researches will be necessary before certainty can be attained in this matter. Meanwhile it seems, from a study of its relations to the Pomeroy or Pittsburgh seam, that what is known as the great vein of the Hocking Valley, occupies the horizon of the Upper Freeport coal, E of the Pennsylvania survey, or No. 6 in Dr. Newberry's enumeration, counting from the base. This seam, in the region in question. assumes certain characteristics which, taken in connection with its geographical position, give it a great importance among the coals of the State. The area to be noticed includes the whole or parts of several townships in Perry, Hocking, Vinton, and Athens Counties, lying near the margin of the basin over which the vein in question assumes the character of a dry-burning or splint coal, and has a thickness varying from six to ten and even twelve feet. Its precise limit southward cannot at present be clearly defined, but it has been found as far south as the line of the Marietta and Cincinnati Railroad, with a thickness of six feet, and is mined at various points along the valley of the Hocking River, near Nelsonville, where it attains six or seven feet. To the northward, along the tributaries of this river, Sunday and Monday

Jan 1, 1874

By T. Sterry Hunt

But little was known of the coals of Southeastern Ohio until the present survey of the State under Dr. Newberry began its work. The results of the geological investigations of Prof. E. B. Andrews in this region, and of the chemical investigations of Prof. T. G. Wormley, both of which appear in the reports of the survey for 1869 and 1874, and more recent special reports by the former, together with some data for which I am indebted to the kindness of Dr. Newberry, and my own limited observations, have served me for the preparation of the following notice of the coals lying on the western border of the great Appalachian coal-basin in the region drained by the Hocking River and its tributaries, and belonging to the Lower Coal-Measures. Some uncertainty exists as to the place in the suc- ' cession of the lower coals to be assigned to the seams known and mined in the Hocking Valley. It is the opinion of Prof. Andrews that the inequalities of the original surface were such that we cannot identify in that region the lowest coals known in Northwestern Pennsylvania and the contiguous parts of Ohio, but that we must rather count from above downwards. These conclusions Dr. Newberry is not prepared to accept, and further researches will be necessary before certainty can be attained in this matter. Meanwhile it seems, from a study of its relations to the Pomeroy or Pittsburgh seam, that what is known as the great vein of the Hocking Valley, occupies the horizon of the Upper Freeport coal, E of the Pennsylvania survey, or No. 6 in Dr. Newberry's enumeration, counting from the base. This seam, in the region in question. assumes certain characteristics which, taken in connection with its geographical position, give it a great importance among the coals of the State. The area to be noticed includes the whole or parts of several townships in Perry, Hocking, Vinton, and Athens Counties, lying near the margin of the basin over which the vein in question assumes the character of a dry-burning or splint coal, and has a thickness varying from six to ten and even twelve feet. Its precise limit southward cannot at present be clearly defined, but it has been found as far south as the line of the Marietta and Cincinnati Railroad, with a thickness of six feet, and is mined at various points along the valley of the Hocking River, near Nelsonville, where it attains six or seven feet. To the northward, along the tributaries of this river, Sunday and Monday

By John L. Boardman

BECAUSE of the attention that has recently been given to the health and safety of miners by various organizations such as the A.I.M.E., The American Congress, Mining Section, National Safety Council, as well as the Bureau of Mines and various state mining departments, your committee on health and safety deemed it best to call attention this year to the mine-accident cause that is by far the most important; namely, injuries due to falls of ground, rock, roof and coal. Each of several members of the committee contributed a brief outline of the importance of this accident cause in his district. While these papers were brief, it would require too much time and space to give them in full, therefore we present an outline of each and summation of all. REPORT OF M. D. COOPER, HILLMAN COAL AND COKE CO. M. D. Cooper, Division superintendent, Hillman Coal and Coke Co., Pittsburgh, Pa., contributed the following: During the period from 1930 to 1939. accidents from falls of roof in bituminous mines average 54.3 per cent of all accidents. In mechanized mining, there is a tendency toward reduction in this class of accidents because the operator of the machine is usually at a distance of 10 to 20 ft. from the face, whereas in hand loading the miner is close to the face during most of the shift. No doubt the use of aluminum and light steel beams supported at regular intervals by jacks, a common practice in mechanical mining, has contributed to the favorable record so far developed. REPORT OF M. H. FIES, DE BARDELEBEN COAL CORPORATION Milton H. Fies, Vice-President, DeBardeleben Coal Corporation, Birmingham, Ala., says: With reference to the types of mining, it is suggested that a clear understanding be had as to the character and thickness of the directly overlying strata, with especial consideration to the strength and in some cases an analysis of it. In coal mining, generally speaking, overlying strata higher in silica than others is stronger. In changing from narrow to wide places, the procedure should be experimental, both as to the width and depth of places and as to the nature of the necessary timbering. Since most of the accidents in coal mining particularly are due to falls of roof and coal, this phase of mining should be attacked with vigor There is no substitute for discipline and, in this connection, under present conditions it is important that cooperation by the labor organizations be sought and that a spirit of fairness prevail. Frequent and thorough inspection of all active working places should be made.

Jan 1, 1941

By J. Russ, C. L. Clark

For many years attempts have been made to develop a laboratory test that would serve to indicate the proper temperatures to be used in the various hot-working applications to which metals may be subjected as they are being processed from the cast ingot to the desired finished products. That these attempts have not been very successful is indicated by the fact that most of the temperatures in use today in these operations have been developed over a period of years by trial and error. In other words, the selection of the proper temperatures for the hot-working of metals is generally an art rather than a science. Our knowledge with respect to the behavior of metals at elevated temperatures has been greatly extended during the past several years. While most of the work in this field has been done at proposed operating temperatures of equipment, rather than at processing or fabricating temperatures, one outstanding fact has been developed, which is applicable to the entire high-temperature range; that is, that the rate of deformation to which the metal is subjected is of the same order of importance as the temperature. The failure to properly recognize this fact has greatly retarded the development of a suitable laboratory test for determining hot-working temperatures. Influence of Rate of Deformation on High-temperature Properties It is not the intent of this paper to survey all the work that has been done On the effect of deformation rate On the properties of metals. The importance of this factor, however, was shown by Zay Jeffries' as early as 1919, when he called attention to the existence of the so-called equicohesive temperature and to the effect of certain factors on the location of this temperature' Fig. I is a diagrammatic sketch showing the effect of temperature On the relative strength of the crystals and grain boundaries and the type of fracture that will res depnding On the location of the test, or Or temperature with respect to the equicOhesive temperature. Since the type fracture varies, it also follows that at temperatures below the equicohesive temperature the major deformation occurs in the grains: while at temperatures above, the deformation results either from the movement of the grains with respect to each other or recrystallization of the strained material occurs almost instantaneously, producing new crystals at the fracture. As previously indicated, it is an established fact that the position of this equicohesive temperature for any given metal is dependent On the deformation rate' For example, in 0.15 per cent plain carbon steel the location of this temperature under

Jan 1, 1947

By C. L. Clark, J. Russ

For many years attempts have been made to develop a laboratory test that would serve to indicate the proper temperatures to be used in the various hot-working applications to which metals may be subjected as they are being processed from the cast ingot to the desired finished products. That these attempts have not been very successful is indicated by the fact that most of the temperatures in use today in these operations have been developed over a period of years by trial and error. In other words, the selection of the proper temperatures for the hot-working of metals is generally an art rather than a science. Our knowledge with respect to the behavior of metals at elevated temperatures has been greatly extended during the past several years. While most of the work in this field has been done at proposed operating temperatures of equipment, rather than at processing or fabricating temperatures, one outstanding fact has been developed, which is applicable to the entire high-temperature range; that is, that the rate of deformation to which the metal is subjected is of the same order of importance as the temperature. The failure to properly recognize this fact has greatly retarded the development of a suitable laboratory test for determining hot-working temperatures. Influence of Rate of Deformation on High-temperature Properties It is not the intent of this paper to survey all the work that has been done On the effect of deformation rate On the properties of metals. The importance of this factor, however, was shown by Zay Jeffries' as early as 1919, when he called attention to the existence of the so-called equicohesive temperature and to the effect of certain factors on the location of this temperature' Fig. I is a diagrammatic sketch showing the effect of temperature On the relative strength of the crystals and grain boundaries and the type of fracture that will res depnding On the location of the test, or Or temperature with respect to the equicOhesive temperature. Since the type fracture varies, it also follows that at temperatures below the equicohesive temperature the major deformation occurs in the grains: while at temperatures above, the deformation results either from the movement of the grains with respect to each other or recrystallization of the strained material occurs almost instantaneously, producing new crystals at the fracture. As previously indicated, it is an established fact that the position of this equicohesive temperature for any given metal is dependent On the deformation rate' For example, in 0.15 per cent plain carbon steel the location of this temperature under

Jan 1, 1947

By L. D. Fetterolf, G. T. Mahler, W. M. Peirce, R. K. Waring

UNTIL recently, the only commercial method of producing magnesium has been fused salt electrolysis, despite a considerable amount of experimental work on the direct reduction of magnesium oxide. In this early work, a number of investigators demonstrated that magnesium oxide would react with any one of several reducing agents to produce magnesium vapor, but that the mixture of magnesium oxide and reducing agent must be heated to a high temperature even in a vacuum. In particular, it was demonstrated that silicon and aluminum are effective reducing agents and that when either of these is used the magnesium vapor can be condensed to massive metal. In spite of this knowledge, no successful commercial reduction process was developed, at least in this country, because of the operational difficulties imposed by the requirement of high temperature and vacuum and because of the high cost of the reducing agent. The outstanding experimental work done by Pidgeon, who carefully reviewed all of the known methods of making magnesium and then selected ferrosilicon reduction, overcame some of the operational difficulties. The process developed by Pidgeon comprises briquetting a mixture of calcined dolomite and reducing agent, pre-heating the briquets to about 600°C. in an externally heated alloy retort, reducing the MgO with silicon in an evacuated horizontal alloy retort heated externally to about 1150°C., and condensing the magnesium vapor to a solid in a cold extension of the retort projecting beyond the fr6nt of the furnace. A major advantage of Pidgeon's process is that the retort is not cooled down between charges. Earlier investigators had used apparatus that necessitated cooling and reheating of the retort between charges. Early in January 1942, when the War Production Board was considering the Pidgeon process for quickly increasing the production of magnesium, The New Jersey Zinc Co. offered to have a research investigation of the process carried on, with the hope of assisting in its further development. This offer was accepted, and a two-retort pilot plant was built at Palmerton and put in operation on Jan. 29, 1942. An intensive investigation of certain phases of the process was carried out in the ensuing four months. This investigation was completed in the last part of May 1942, and the pilot plant was then shut down. Subsequently, The New Jersey Zinc Co. was requested to have further development work done on the process, and a more extensive investigation was undertaken in August I942 under contract with the War production Board and under the super- vision of the War Metallurgy Committee. This paper describes the phases of the investigation that are thought to .be

Jan 1, 1944

By Enid C. Plante

This paper deals with the flotation of the mineral fluorite (calcium fluoride) and of two associated gangue minerals, calcite and quartz. The aim of the investigation was to produce "acid-grade" fluorite, which must contain less than one per cent of silica. Several reagents are used successfully in practice for floating fluorite from its ores. Oleic acid is the most widely used collector, usually at temperatures above 60°C, with sodium silicate as a dispersant for quartz and quebracho or tannin to depress calcite. Sulphides (e.g., galena) are often removed first by xanthate flotation. Many investigators23 report results in which more than 80 pct of the fluorite is recovered in a concentrate assaying 96 pct or more of fluorite and less than I pct of silica. This investigation was undertaken with the intention of floating the gangue, which is the minor constituent of the ore, from the fluorite. Hence emphasis was first placed on the cationic compounds that float quartz. No satisfactory separations were obtained in this way, and other reagents were investigated to discover whether these were more effective than oleic acid in floating fluorite from quartz in the usual way. The first part of the paper describes experiments with several long-chain collectors available commercially. Most of this work has been by captive-bubble and cylinder flotation tests, with some batch tests in a flotation machine. The second part describes the use of sodium cetyl sulphate as a collector for fluorite and includes laboratory tests and extension of the work to batch tests in the flotation machine. A method for determining the adsorption of sodium cetyl sulphate on fluorite has been developed and is described. Theory of Collection by Paraffin-chain Salts It may be assumed that these compounds are adsorbed at the mineral surface in one or more of three ways outlined by Kolthoff:12 1. Exchange adsorption between lattice ions in the mineral surface and collector ions in solution. Closely related is adsorption by the collecting mechanism postulated by Taggart,17 in which there is metathesis between the collector and the mineral cation or anion. 2. Exchange .adsorption between adsorbed gegen ions (p. 67, ref. 19) and collector ions in solution. 3. Adsorption of nonelectrolytes (polar-nonpolar) without displacement of adsorbed ions. With cationic collectors, inorganic cations in the solution (e.g., hydrogen ion) compete with the collector ions and therefore act as depressants, while inorganic anions have the same effect with anionic collectors. From this follows the general conclusion that ions of the same charge as

Jan 1, 1949

By L. W. Davies

A problem often encountered is the provision of materials which have impurity contents below a certain specified level. This problem is in some cases solved by making use of the segregation of the impurity with respect to the liquid and solid states of the material: an ingot of the material is subjected to directional solidification and the ends of the ingot. which are richer in solutes which respectively raise and lower the melting point of the solvent, are removed. An important extension of this process is the zone-refining process invented by pfann,' in which molten zones are passed successively along the length of an ingot and displace solutes towards the ends. Pfann's process is particularly appropriate in cases for which the segregation coefficient k does not differ greatly from unity, or when the impurity content must be kept extremely low (-=,6 atom fraction); it is widely used, particularly in the purification of materials for use in semiconductor electronic devices. It is the purpose of this paper to investigate theoretically the efficiency of the above refining processes; that is! we determine the most economic method of attaining a given yield of solvent of specified purity, taking into account the variables of the process. One variable of interest is the effective value of the segregation coefficient. which depends on the rate of movement of the liquid-solid interface and on the degree of stirring in the liquid; in addition to this, in the zone-refining process we are also interested in the choice of zone length for most efficient operation. A mathematical determination is made here of the lengths of successive molten zones which give, for an initially uniform distribution, the most efficient removal of a solute of arbitrary distribution coefficient. In order to be able to give a quantitative treatment of efficiency, we first define figures of merit applicable to a given distribution of solute. FIGURE OF MERIT Let an ingot of length L contain a distribution y(x) of solute: we confine our discussion to mono-tonic distributions, in order to avoid inconsistencies in the subsequent analysis. The first moments of the distribution about the origin and x = L are respectively L F = hy{x)dx [I] G = f(L -x)y(x)dx = YoL2-F, [21 where yoL is the total amount of solute present. We shall see that the quantities F and G are useful figures of merit for a discussion of the efficiency of zone-refining processes. In the first place, it is

Jan 1, 1960

By L. W. Davies

A problem often encountered is the provision of materials which have impurity contents below a certain specified level. This problem is in some cases solved by making use of the segregation of the impurity with respect to the liquid and solid states of the material: an ingot of the material is subjected to directional solidification and the ends of the ingot. which are richer in solutes which respectively raise and lower the melting point of the solvent, are removed. An important extension of this process is the zone-refining process invented by Pfann,' in which molten zones are passed successively along the length of an ingot and displace solutes towards the ends. Pfann's process is particularly appropriate in cases for which the segregation coefficient k does not differ greatly from unity, or when the impurity content must be kept extremely low (=10-6 atom fraction); it is widely used, particularly in the purification of materials for use in semiconductor electronic devices. It is the purpose of this paper to investigate theoretically the efficiency of the above refining processes; that is! we determine the most economic method of attaining a given yield of solvent of specified purity, taking into account the variables of the process. One variable of interest is the effective value of the segregation coefficient. which depends on the rate of movement of the liquid-solid interface and on the degree of stirring in the liquid; in addition to this, in the zone-refining process we are also interested in the choice of zone length for most efficient operation. A mathematical determination is made here of the lengths of successive molten zones which give, for an initially uniform distribution, the most efficient removal of a solute of arbitrary distribution coefficient. In order to be able to give a quantitative treatment of efficiency, we first define figures of merit applicable to a given distribution of solute. FIGURE OF MERIT Let an ingot of length L contain a distribution y(x) of solute: we confine our discussion to mono-tonic distributions, in order to avoid inconsistencies in the subsequent analysis. The first moments of the distribution about the origin and x = L are respectively L F = hy{x)dx [I] G = f(L -x)y(x)dx = YoL2-F, [21 where yoL is the total amount of solute present. We shall see that the quantities F and G are useful figures of merit for a discussion of the efficiency of zone-refining processes. In the first place, it is

Jan 1, 1960

By W. H. Blauvelt

W. H. BLAUVELT, Syracuse, N. Y. (communication to the Secretary*).-I have read Mr. Howland's paper on Calculations with Reference to the Use of Carbon in Modern American Blast Furnaces with much interest, and believe that his method of analysis of the subject will be of material assistance in our study of the action of coke in the blast furnace. Mr. Howland quotes Professor Richards' statement that from the standpoint of the generation of the maximum quantity of heat in the furnace, Grüner was right in saying that all the carbon burned in the furnace should be first oxidized at the tuyères to CO and all reduction of oxides above the tuyères should be caused by CO, which thus becomes CO2. It is clear that the maximum quantity of heat is generated in the furnace when the greatest amount of carbon is burned to CO2 irrespective of whether it is burned at the tuyères or further up the furnace. So it would appear that Grüner's theory is sound regarding the maximum production of heat only because if all the carbon is burned to CO at the tuyères the reduction of the ores will have to be effected by the further oxidation to CO2. Whereas, if the reduction of the ores is effected in part by solid carbon, part of this carbon might be oxidized only to CO, resulting in a higher percentage of CO in the escaping gases than from Grüner's "ideal conditions.? But in studying the combustion of coke in the furnace, it is clear that the production of the maximum quantity of heat is not of the first importance in blast-furnace operation, or in the utilization of the fuel charged into the furnace. To my mind the production of a high thermal head at the tuyères is of the first importance, and the best coke is that which reaches the tuyères in proper condition to produce the highest temperature at the tuyères, and in just sufficient quantity to do the amount of work required there under the conditions produced by this maximum temperature. The combustion of a much larger amount of fuel at the tuyères, under conditions that will fall short of producing the highest possible temperature, cannot produce as good results, either in fuel economy or output. If this statement is correct, does it not correspond with Mr. Howland's statement that too much wind is inimical to low coke consumption? Nothing is more fatal to obtaining the highest temperatures than an excess of air for combustion. In the blast furnace an excess of air dilutes and cools the products of combus-

Jan 10, 1916

By L. Casagrande, C. O. Brawner, D. L. Pentz, B. Kennedy, E. Hoek, H. Q. Golder, K. Barron

H. L. HAMMERSLEY, B. C. Dept. of Mines. I would like to ask Mr. Brawner if the direction that he measured in the boreholes with the camera was referenced to magnetic north? MR. BRAWNER. Yes, it was. However, there is one problem that you may encounter if the ore body is magnetic; the borehole compass will give erroneous results. Three procedures are available to overcome this. The first one involves the use of a gyro compass instead of a magnetic compass. The second technique developed by Christiansen in Salt Lake City, is to orient the core with the use of scribing knives. The third method is to remove the compass needle and place a steel ball in the compass case. The hole must be drilled at a slight angle off the vertical. The location of the steel ball, which will roll to the underside of the hole is photographed. A borehole directional survey is then made, from which the bearing of the steel ball relative to the axis of the compass can be determined. The joint orientation is then related to this bearing at all depths. J. ROBINSON, B. C. Dept. of Mines. It was stated this morning that there have been some recent developments that give us the ability to drill horizontal drainage holes and install drainage pipes more cheaply than in the past. Would Mr. Brawner tell us some of the new developments and methods of installing these horizontal drain holes? MR. BRAWNER There are two zones in which you may be concerned about installing drains; the first is in the overburden soil, the second is in the rock. Each area requires a different installation method. If the rock is fairly massive and the holes will remain open, the simplest procedure is to use standard air track equipment or a percussion drill. At one of the mines in the Highland Valley, drains up to 300 ft. long have been installed with a percussion drill at a rate of one drain per day. The costs were in the order of $2.30 and $2.40 per foot. If the rock is quite soft, such as in a serpentine, it will be necessary to install a casing in the hole. The least expensive casing that will not deteriorate within the life required should be used. Plastic pipe or black iron pipe are commonly used. In soft rock, it may be necessary to drill with a casing to prevent the col-

Jan 1, 1971

By Helmut Thielsch

During the last three decades a great many arguments have been presented on the subject of "mosaicJ' or "blockJJ structures of metals. Apparently because of insufficient evidence, the "block-structure" theories have never been widely understood among the physical metallurgists in this country, and most investigators among the few that have tried to demonstrate the existence of such an inner strutture Of crystals or grains have failed to recognize also the existence of a lamellar structure. Moreover, little thought has been given to justify the existence of such "lamellar" or "mosaic-block" structures on a theoretical basis. Since properties such as Plasticity; ferro-magnetism, hardness, diffusion, and others may be explained by structural faults in the lattice network of the crystals: the great importance of a more detailed knowledge of the structure within crystals or grains becomes now evident. Because Of the vast extent of the field Of submicroscopic structures, it shall be the purpose Of this paper only to review the more important of the results obtained by other investigators, especially in Germany, where a great deal of attention has been given to mosaic structure during the last three years. The origin of this mosaic patternt and effects of cold reduction and recrystallization will be shown in further studies later on. Imperfections in Crystals The many terms used in the literature to denote structural types of crystals are often not clearly defined. To clear up some of the confusion, the meaning of the more important terms will be given here. ideal, or perfect without any structural imperfections are called "ideal crystals,,or ''Perfect'' crystals,n meaning a Homogeneous interior structure of atoms, ions or molecules, as the case may be. In other words, at every point in the interior of the crystal exactly the same orientation of the crystallographic axes of the coordinate system would exist. The Surface of such a body, if etched with an appropriate etching reagent, would reflect light with perfect uniformity. Crystals of this type are almost nonexistent. Real Crystals.—L'Real crystals"' may contain various types of structural defects, which can be classified into: (I) lineage structure, (2) mosaic-block structure, (3) lamellar structure. The inhomogeneities many,in these groups mean that the orientation of the crystallographic aies will not be the same at every point within the interior of a crystal (or grain of a poly crystalline body). 'Perjecl Real Crystals.—The term "perfect real crystals " is generally used to describe crystals with minute structural or thermo-dynamical inhomogeneities. The former

Jan 1, 1946

By Y. L. Yao

It is suggested that the binary alloy systems of transition metals may be classified into groups according to "excess energy"E. For systems with positive ?E, the Laves phase, the TiNi3-, the TiCu3- and the Cudu-type rich in the smaller atom and the TizNi-type rich in the larger atom may exist. For systems with negative ?E and composed of two components of different crystal structures, the X, the Cr3O and the phase may exist on the side of the phase digrattz rich in the component with the higher "solubility factor" value am! the Cudu-type and the disordered hcp phase on the other side; if the crystal structure of two components is the same, the Cudu-type may exist on both sides. For systems with weakly positive ?E and cotnposed of different crystal structures, the u phase and the MgCd3-type may replace the Laves phase and the other types; the X, the Cr3O and the a phase may also exist. Finally, the equirnolar compounds of the CuAu- and the CsC1-type may exist irrespective of the sign of ?E. THERE are many factors which play a major role in the formation of binary intermediate phases in alloys, such as the crystal structure, the electronic structure, the atomic size and the electrochemical factor. To find the simultaneous effects of all these factors on the formation of intermediate phases of every metal would be a difficult task, especially because only a small fraction of experimental facts necessary for the complete formulation is known at present. Thus the past surveys of intermediate phases have been usually confined to few metals, several types of intermediate phases and some but not all controlling factors. In a previous paper1 the idea of "solubility factor" of metals was introduced. Although the suggested values are tentative and empirical, the formation of a continuous series of solid solutions in metals could be correlated with the interplay among the atomic size factor, the solubility factor and the crystal structure factor. The purpose of this paper is to demonstrate qualitatively the interplay of these factors in the formation of binary intermediate phases among transition metals. FACTORS CONSIDERED The Crystal Structure Factor. With rare earths excluded, the transition metals are classified into three common crystal structures listed in Table I. There is arbitrariness in the present classification of several allotropic elements. However, out of seventy-odd continuous solid solutions formed among transition metals, only six of them, namely, those

Jan 1, 1962

By O. N. Cole, R. E. Davis, T. D. Brotherton

Pvfoperties of rubidium and cesium are compared with those of other alkali metals. Methods for the preparation of rubidium and cesium metal are reviewed briefly, ad hazards and safety precautions required in handling rubidium and cesium metal are described. SimPle methods for handling laboratory quantities of elemental rubidium ad cesium under oil and under argon are illustrated. CESIUM and rubidium were both discovered by Bunsen and Kirchoff in the years 1860 and 1861. Cesium was discovered while Bunsen and Kirchoff were making a spectrographic study of spring water from Durkheim, Germany. It was the first element discovered by this technique. The element was given the Latin name "caesius" for sky blue because of the color it imparted to flames. Elemental cesium was first prepared by Setterberg in 1881 through electrolysis of a molten mixture of cesium and barium cyanides.' In 1861, Bunsen and Mirchoff discovered rubidium while making a spectrographic study of the alkali content of lepidolite ore from Saxony. Two prominent dark red lines appeared in the spectrum and so the element was named "rubidius" or dark red. In 1861 Bunsen and Kirchoff first prepared elemental rubidium through the electrolysis of molten rubidium chl~ride.~ The alkali metals are very similar in their chemical and physical properties. They are the most active metals, and all exhibit a single oxidation state of one. They are so reactive that they are never found in nature in the elemental state. The reactivity of he metals increases with atomic number. Rubidiurn and cesium ignite spontaneously in air and react explosively with water. This extreme reactivity makes necessary special equipment and techniques for the safe preparation and use of the metals. The cation: of Group IA can be separated from the metallic cations of other groups with relative ease, but the separation of the individual alkali cations is much more difficult because of their close chemical similarity. This close chemical and physical similarity of alkali metals can be inferred from the atomic radii, oxidation numbers, and ioni-zation potentials shown in Table I. A difficult but the most practical physical method of separating the elemental alkali metals from one another is by distillation. Only lithium has a boiling point sufficiently far-removed from the boiling points of the other alkali metals to make this method of separation feasible without elaborate and expensive equipment. This method is not used, however, for lithium because it possesses sufficient chemical dissimilarity from the other alkalies for it to be separated relatively easily as lithium hydroxide monohydrate or as lithium carbonate. Francium, the last member of the group, has no known stable isotopes. The naturally occurring

Jan 1, 1962